We first came upon this method of building while having a midlife crisis, buying 120 acres of forest and building a Sustainable Living business. We sought the advice of a friend who showed us a half-built workshop using a tyre-earth construction. We were instantly attracted to its deep walls and window seats, the free flowing lines possible, and the solid, part-of-the-earth feeling it had. We knew we wanted to build using recycled materials, that would have an organic flavour, but had decided that mud brick was probably beyond us. Our friend had done mud brick buildings as well as this new method, and had found the latter easier on old backs. The idea of being able to recycle the tyres in such a useful way really appealed to us. Full engineering specs were available, and our council passed our plans. Their attitude was very helpful, once they stopped laughing.
Economically, this is a good way to go. Obviously, used tyres are free. Our local tyre retailer trucks them out for us when he has a hundred or so of the size we want, and is happy to do so since otherwise he would have to pay to dispose of them. The earth on our block passed its testing and is fine to use, and all we pay for is the cement we use to mix with the earth. There you have your walls. Recycled windows and timbers blend beautifully with the earthen walls, as in all other earth building techniques.
It is heavy work, of course, but very satisfying. The wet earth mixture is packed into the tyres and into the gaps between tyres, and seeing the shape of the walls evolve, feels a bit like making a cubby house did when we were kids. On hot days, or when we are very tired, we can mix earth, cement and water in the cement mixer and simply spend the day packing spaces between the tyres, a cool and not too taxing process. We built a small cabin first, before starting work on the house. We have learned our trade, so to speak, on this smaller building, and developed our routines and techniques.
The tyres, empty, are laid out along the slab, and eventually one layer on top of another, as you would place bricks or blocks. Each tyre is then rammed with as much earth as can be made to fill it. The advantage of the tyres over conventional rammed earth is that your formwork remains in place, forever hidden, giving additional stability to the wall. The original US developed method entails ramming dry earth into the tyres using a sledge hammer. We tried this on our first ten tyres and quickly realised there had to be a better method. Our bodies couldn’t take the jarring. We experimented a bit and found that a stabilised wet mud brick mixture hand rammed into the tyres worked better, finishing off by pounding more dry earth in on top. This results in a rock hard wall. The final finish on the walls will be a mud render covering. The tyres are completely sealed within the wall, and not visible or able to decompose in the sunlight. This gives a wall surface similar appearance to other earth built homes, but a much thicker wall, which is an obvious advantage in cold areas.
A further advantage of tyre-earth construction over mud brick is that you are only handling the material once, because you make the walls as you go instead of making the bricks and then building the walls. We have made a lot of mud bricks as well, for use as garden steps, so we know which is easier for us. The shapes of the walls are only limited by your imagination and the constraints of your particular block. The tyre walls are load-bearing, and can be used to create some wonderful free form effects.
We decided on a corrugated iron roof. Recycled material featured high in our priorities, as did the look of large beams forming the main structural components of the house. We found the remains of an old railway bridge that had timbers very suitable for our needs at a nearby demolition yard.
The beams were attached to the walls with 2m long threaded rods that were included into the tyre walls as they were built. This was part of the fun in placing the beams as they had to be threaded over the rod as they were lowered into place. We almost got it right. All the beams lower smoothly into place except one, there is always one. As the crane was rather expensive, this one was lowered onto wooden blocks, redrilled and then lowered down onto the tyre wall using a car jack.
Undertaking the final plastering of the walls to cover the tyres also involved undertaking a range of experiments. We needed to ensure that we achieved a nice smooth finish, which provided a robust surface immune to being bumped and scratched, and also resisted water. Many experiments with different mixes eventually lead us to a wall surface we were happy with. The earth was sifted using a garden sieve to get rid of all the larger gravel in the soil. We experimented using a range of propriety products, linseed oil, lime and different quantities of cement. Eventually we found a mix of the local soil with 10-15% cement in a fairly soft mixture and applied with lime wash brushes worked extremely well. Many people recommended to us that the walls should lined with chicken wire to had strength to the plaster. However we found in general that as long as the tyres had a good tread still we seam to get a better adhesion of the plaster without the wire. In places we found that the wire inhibited the plaster gripping the walls. The walls were finally finished with a natural stone sealant to give them a little water resistance and make them easier to clean.
Before applying the final plaster we had to think about where we wanted plumbing and wiring. These need to be fitted in the walls before the final plastering is completed. The water plumbing was fixed to the tyres before being plastered over. The plumbing in particular made any irregularities in the walls stand out and how important it is to ensure that the walls are vertical. Our walls were designed to be 70 cm thick. We ended up in places with walls somewhat thicker than this due to our inexperience and the need to have the shower-head over the top of our heads.
Stud walls were used for the internal walls mainly due to the need to conserve space. The tyre walls being so thick and the building site being steep, using tyre walls internally would have meant a significant increase in the size of the floor slab and foundations and also the size of the excavations. The stud walls were fixed to the external walls by screwing them to the tyres before they were plastered.
The windows and doors we had been lucky enough to find at a demolition yard before we started building. This made it very easy to know how big the spaces needed to be. While we were building we made a frame the size of the window or door to make the space in the wall. This frame was fixed to the surrounding tyres using strapping. When we had finished all we had to do was slide the window or door into the frame in the wall and fix it to the frame. The bridge beams except for one window in the gable ends where we used old ironbark railway sleepers formed lintels for the windows and door.
The last three years has seen us learn a whole range of skills from ramming earth to various skills in carpentry, rendering, plastering, tiling and concreting. Using the tyres has proven very simple with no special skills needed except a lot of hard labour. We did learn how important it is that your local tyre merchant supply uniform sized tyres or else it is very easy to get the walls out of kilter. Inexperience resulted in some irregularities in the walls which can be solved by thickening the render but greater attention to laying the tyres would solve this problem. On a number of occasions we learned the benefits of planning ahead or, in our case, not planning ahead. Again this is learnt from experience or having someone to regularly talk to as things progress. This is mainly knowing what needs to be built into the walls like roof ties, pipes and cabling and power points.
On top of all this, we get a great deal of satisfaction from knowing that we have recycled many more tyres than we have used on cars that we have owned. This adds a whole new dimension to our sustainable home!
Tags: Rammed Earth Tyres Earthship
